Motion Segment Repair Systems and Methods

ABSTRACT

Various methods and devices are provided for implanting a motion segment repair system. In particular, exemplary methods and devices are provided for implanting a spinal disc implant and/or a PDS device using a posterior surgical approach, including methods and devices for distracting adjacent vertebrae using a posterior surgical approach, methods and devices for posteriorly introducing a spinal implant into a disc space between adjacent vertebrae, and methods and devices for coupling a PDS device to the adjacent vertebrae to provide a complete motion segment repair system that is implanted using a posterior surgical approach.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/164,643 filed on Nov. 30, 2005 and entitled “Methods of Implanting aMotion Segment Repair System,” which claims the benefit of U.S.Provisional Application No. 60/721,603, filed Sep. 9, 2005. Thesereferences are hereby incorporated by reference in their entireties.

BACKGROUND

Disease, advancing age, and trauma can lead to changes in various bones,discs, joints, and ligaments of the body. Some changes and trauma oftenmanifest themselves in the form of damage or degeneration to a spinaldisc. This condition often results in chronic back pain, which can beanywhere from mild to severe. This pain can sometimes be eliminated byspinal fusion in which two adjacent vertebral bodies are jointedtogether after removing the intervening intervertebral disc. Aprosthetic device is usually placed between the two adjacent vertebralbodies, in place of the removed disc, to fill the space left by theremoved disc and to allow bone to grow between the two vertebral bodies.

More recently, spinal implants, referred to as posterior dynamicstabilizers, have been developed that allow motion between the adjacentvertebrae, thereby restoring normal function to the vertebrae. Whilethese implants have been met with great success, they typically requirean anterior surgical approach to be used to position the implant betweenadjacent vertebrae so as to avoid contact with the spinal cord. Theimplant sizes and instrumentation also dictate an anterior approach tothe spine. Most anterior surgical approaches, however, tend to beinvasive due to the nature and amount of the anatomy that needs to bedisplaced in order to successfully access the disc space. Moreover, thesurgical procedure typically requires a general or vascular surgeon toexpose the spine, and a spinal surgeon to perform the discectomy andimplantation, thereby increasing the costs. Post-operative complicationscan also occur during an anterior surgical approach, including abdominalwall hematoma, vascular injury, retrograde ejection, andgastrointestinal injury.

Accordingly, there remains a need for improved methods and devices forposterior dynamic stabilization, and in particular for a full motionsegment repair system and methods for implanting the same using aposterior or posterior-lateral approach.

SUMMARY

The present invention generally provides methods and devices forimplanting a motion segment repair system using a posterior orposterio-lateral approach. In one exemplary embodiment, the method caninclude implanting a disc implant between adjacent superior and inferiorvertebrae using a substantially posterior surgical approach and couplinga posterior stabilization device to the adjacent superior and inferiorvertebrae. At least one of the disc implant and the posteriorstabilization device can have a floating center of rotation to allow theposterior stabilization device to be positioned at various locationsrelative to the adjacent superior and inferior vertebrae, and to allowand/or control flexion, extension, lateral bending, axial rotation,and/or anterior-posterior shear between the adjacent superior andinferior vertebrae.

In one embodiment, the disc implant can have a floating center ofrotation. For example, the disc implant can include first and second endplates with a central core moveably disposed there between. In otherembodiments, the disc implant can have a fixed center of rotation. Inanother embodiment, the posterior stabilization device can have afloating center of rotation. For example, the posterior stabilizationcan include a first connector that couples to a superior vertebra and asecond connector that couples to an adjacent inferior vertebrae. Thefirst and second connectors can be movably mated to one another by aflexible member to allow and/or control flexion, extension, lateralbending, axial rotation, and/or anterior-posterior shear between theadjacent superior and inferior vertebrae. In yet another embodiment, theposterior stabilization device can have a fixed center of rotation. Forexample, the posterior stabilization device can include a firstconnector that couples to a superior vertebra and a second connectorthat couples to an adjacent inferior vertebrae. The first and secondconnectors can be slidably coupled to one another to allow flexion andextension between the adjacent superior and inferior vertebrae.

In another exemplary method for implanting a motion segment repairsystem, adjacent superior and inferior vertebrae can be distracted usingat least one distraction anchor disposed in a posterior side of each ofthe adjacent superior and inferior vertebrae. A disc implant can beinserted between the adjacent superior and inferior vertebrae. A bonescrew can be implanted over each distraction anchor and a posteriorstabilization device can be coupled to the bone screws to couple theadjacent superior and inferior vertebrae to one another. In an exemplaryembodiment, first and second distraction anchors can be implanted onopposed lateral sides of the superior vertebra, and third and fourthdistraction anchors can be implanted on opposed lateral sides of theinferior vertebra. The adjacent superior and inferior vertebrae can bedistracted using a spreading device that engages the distractionanchors. The disc implant is then inserted using a substantiallyposterior surgical approach.

In another exemplary embodiment, the distraction anchors can be used tore-distribute a load applied to the implant to move the implant in aposterior direction. For example, tension can be applied to a member,e.g., a guidewire, coupled to the disc implant to move the disc implantin a posterior direction while distributing the load along an axis ofthe distraction anchors. In particular, the member can be coupled to oneor more supports extending between the distraction anchors. In anexemplary embodiment, the supports have first and second bores forreceiving the distraction anchors, and a third bore for slidablyreceiving a guidewire therethrough.

Exemplary methods for implanting a disc implant using a posteriorapproach are also provided. In one embodiment, the method can includeintroducing a disc implant to an anterior location between adjacentsuperior and inferior vertebrae using a substantially posterior surgicalapproach, and pulling the disc implant in a posterior direction toposition the disc implant between then adjacent superior and inferiorvertebrae. For example, tension can be applied to a guidewire coupled tothe disc implant to move the disc implant in a posterior direction.Pulling the disc implant in a posterior direction is effective todistract the adjacent superior and inferior vertebrae. The method canfurther include coupling a posterior stabilization device to theadjacent superior and inferior vertebrae. In another embodiment, thedisc implant can be introduced between the adjacent superior andinferior vertebrae using a guide device. The guide device can bepositioned on a posterio-lateral side of a spinal column to guide thedisc implant medially between adjacent superior and inferior vertebrae.For example, the disc implant can be moved along a curved pathway formedon the guide device to position the disc implant between the adjacentsuperior and inferior vertebrae. The guide device can optionally includea pivoting member formed thereon to position the implant between theadjacent superior and inferior vertebrae and to pivot the implant toposition it between the adjacent vertebrae.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a prior art motion segment repair systemimplanted between two adjacent vertebrae;

FIG. 2 is a perspective view of a disc implant of the prior art motionsegment repair system shown in FIG. 1;

FIG. 3 is a perspective view of one exemplary embodiment of a prior artposterior stabilization device;

FIG. 4 is a side view of one exemplary method for distracting twoadjacent vertebrae using distraction anchors which are configured toreceive bone screws there over;

FIG. 5A is a side view of a prior art distraction device that can beused to engage the distraction anchors shown in FIG. 4 to distract theadjacent vertebrae;

FIG. 5B is a side view of another prior art distraction device that canbe used to engage the distraction anchors shown in FIG. 4 to distractthe adjacent vertebrae;

FIG. 5C is a side view of yet another prior art distraction device thatcan be used to engage the distraction anchors shown in FIG. 4 todistract the adjacent vertebrae;

FIG. 5D is top view of one exemplary method for positioning a two-piecedisc implant between adjacent vertebrae by distracting a first side ofthe disc space and implanting a first portion of the disc implant on asecond side of the disc space;

FIG. 5E is a top view of the vertebrae shown in FIG. 5E, showing asecond portion of the disc implant implanted on the first side of thedisc space;

FIG. 5F is a side view of another exemplary embodiment of a distractiondevice that can be use to facilitate distraction of adjacent vertebrae;

FIG. 6A is a top view of one exemplary embodiment of a method forpositioning a disc implant between adjacent vertebrae using a guide wireand two support members coupled to distraction anchors implanted inopposed lateral sides of each vertebrae;

FIG. 6B is a side view of the adjacent vertebrae shown in FIG. 6A,showing the guide wire and one of the support members;

FIG. 7A is a top view of a prior art device that can be used to insert adisc implant into the disc space between adjacent vertebrae;

FIG. 7B is a side view of the prior art device shown in FIG. 7A;

FIG. 8 is a top view of another exemplary embodiment of a method forinserting a disc implant into the disc space between adjacent vertebraeusing a guide device having a pivoting member formed thereon forpivoting the disc implant into the disc space;

FIG. 9A is a side view of a depth gauge indicator for determining properplacement of a posterior stabilization device based on a depth of a discimplant disposed between superior and inferior vertebrae; and

FIG. 9B is a top view of the device shown in FIG. 9A.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Various exemplary methods and devices are provided for stabilizing theposterior elements of the spine, and more preferably methods and devicesare provided for implanting a spinal disc implant and/or a posteriordynamic stabilization (PDS) device using a posterior or posterio-lateralapproach. In particular, exemplary methods are provided for distractingadjacent vertebrae using a posterior approach, posteriorly introducing adisc implant, and coupling a PDS device to the adjacent vertebrae toprovide a full motion segment repair system. A person skilled in the artwill appreciate that the term “posterior approach” as used herein isintended to include both posterior and posterio-lateral approaches.

Disc Implants and PDS Devices

The disc implant and PDS device used with the various methods anddevices disclosed herein can have a variety of configurations, andvirtually any disc implant and PDS device known in the art can be used.In an exemplary embodiment, however, the disc implant and the PDS deviceare configured to allow at least some movement between adjacentvertebrae coupled thereto, and more preferably at least one device has afloating center of rotation. In particular, one or more joints on thedisc implant or PDS device can be configured to allow movement along acenter of rotation that moves and thus is not fixed. The other one ofthe disc implant and PDS device can likewise have a floating center ofrotation, or it can have a fixed center of rotation. The use of a discimplant and PDS device having at least one floating center of rotationallows the PDS device to be implanted at various locations relative tothe adjacent vertebrae, whereas a motion segment repair system (i.e.,disc implant and PDS device) that does not have at least one floatingcenter of rotation requires precise alignment of the PDS device with thedisc implant.

FIGS. 1-3 illustrate various exemplary embodiments of a prior art discimplant (FIG. 2) and prior art posterior stabilization devices (FIGS. 1and 3) that can be used with the various exemplary methods and devicesdescribed herein. Referring first to FIG. 1, one exemplary embodiment ofa motion segment repair system 10 is shown having a disc implant 60 anda PDS device with a fixed center of rotation. The disc implant 60, whichis shown in more detail in FIG. 2, generally includes superior andinferior endplates 210, 230 and a central core 250 disposedtherebetween. The superior endplate member 210 is adapted to bepositioned adjacent to an endplate of a superior vertebra, and theinferior endplate member 230 is adapted to be positioned adjacent to anendplate of an inferior vertebra. The outer surfaces of the endplatemembers 210, 230 can be configured to complement the shape of thevertebral endplates. The core 250 can be a resilient member that isadapted to be received between the endplate members 210, 230. As aresult, the endplate members 210, 230 can move relative to the core 250to allow movement of the adjacent vertebrae relative to one another. Theimplant 60 is described in more detail in U.S. patent application Ser.No. 11/055,025 of DePuy Spine, Inc., filed on Feb. 10, 2005 and entitled“Intervertebral Prosthetic Disc.” This application is herebyincorporated by reference in its entirety.

While FIGS. 1-2 illustrate a disc implant having a floating center ofrotation, in other embodiments the disc implant can have a fixed centerof rotation. Examples of such implants include fixed core implants andball-and-socket implants.

As previously indicated, FIG. 1 also illustrates one embodiment of aprior art PDS device having a fixed center of rotation. The PDS devicegenerally includes a first member 20 that is coupled to a firstvertebra, e.g., the superior vertebra 60 s, and a second member 30 thatis coupled to a second vertebra, e.g., the inferior vertebra 60 i. Thefirst and second members 20, 30 are movably coupled to one another bysliding pins that are slidably disposed through lateral members. In use,the first and second members 20, 30 cooperate to control movement of thesuperior and inferior vertebrae 60 s, 60 i relative to one another, andin particular they allow at least some flexion, extension, and lateralbending of the vertebrae 60 s, 60 i, while substantially restrictingposterior-anterior shear and rotation of the vertebrae 60 s, 60 i. ThePDS device is described in more detail in U.S. patent application Ser.No. 10/908,882 filed on May 31, 2005 and entitled “Facet JointReplacement.” Other exemplary embodiments of PDS devices having a fixedcenter of rotation are also disclosed in U.S. patent application Ser.No. 10/908,882, as well as U.S. patent application Ser. No. 10/905,376filed on Dec. 30, 2004 and entitled “Posterior Stabilization System.”These applications are assigned to DePuy Spine, Inc., and they arehereby incorporated by reference in their entireties.

As indicated above, in other embodiments the PDS device can have afloating center of rotation, i.e. one or more joints on the PDS devicecan allow movement along a center of rotation that moves and thus is notfixed. FIG. 3 illustrates one embodiment of a prior art PDS devicehaving a floating center of rotation. As shown, the device 310 generallyincludes first and second flexible members 312, 314, also referred to asdynamic stabilizing elements, and first and second connectors 316, 318,also referred to as stabilizing rods. As shown in FIG. 3B, the device310 is coupled to superior and inferior vertebrae 360, 362 such that itis effective to perform the function of the posterior elements thatconnect the vertebrae, or to otherwise control movement of the vertebrae360, 362. More particularly, the first connector 316, hereinafterreferred to as the superior connector 316, is coupled to the superiorvertebra 360, and the second connector 318, hereinafter referred to asthe inferior connector 318, is coupled to the inferior vertebra 362. Thesuperior and inferior connectors 316, 318 extend through the first andsecond flexible members 312, 314, such that the connectors 316, 318 arecoupled to one another via the flexible members 312, 314. As a result,the connectors 316, 318 and the flexible members 312, 314 are effectiveto control movement of the vertebrae 360, 362 relative to one another,thereby functioning in place of the posterior elements. In an exemplaryembodiment, the flexible members 312, 314 are movable, e.g., rotatableand/or slidable, but preferably not deformable, relative to at least oneof the connectors, e.g., the superior connector 316, when the vertebrae360, 362 are moved within a first range of motion, and at least one ofthe connectors, e.g., the superior connector 316, is effective todeform, e.g., stretch, rotate, etc., the flexible members 312, 314, orotherwise create resistance, when the superior and inferior vertebrae360, 362 are moved within a second range of motion beyond the firstrange of motion. As a result, the PDS device 310 has a floating centerof rotation.

Other exemplary embodiments of PDS devices having a floating center ofrotation are disclosed in U.S. patent application Ser. No. 11/160,139filed on Jun. 10, 2005 and entitled “Posterior Dynamic StabilizationX-Device,” U.S. patent application Ser. No. 11/160,143 filed on Jun. 10,2005 and entitled “Posterior Dynamic Stabilization Systems and Methods,”U.S. patent application Ser. No. 10/908,882 filed on May 31, 2005 andentitled “Facet Joint Replacement,” U.S. Pat. No. 10/905,374 filed onDec. 30, 2004 and entitled “Artificial Facet Joint,” and U.S. Pat. No.10/955,207 filed on Sep. 30, 2004 and entitled “Posterior StabilizationSystems And Methods.” These applications are all assigned to DePuySpine, Inc., and they are hereby incorporated by reference in theirentireties.

Methods for Implanting Motion Segment Repair Systems

As previously explained, the present invention generally providesmethods for implanting a spinal disc implant and/or a PDS device, suchas those previously described, using a posterior surgical approach.FIGS. 4-5C illustrate exemplary methods and devices for distractingadjacent vertebrae using a posterior surgical approach, and FIGS. 6A-9Billustrate exemplary methods and devices for posteriorly introducing aspinal implant into a disc space between adjacent vertebrae. Exemplarymethods can also include coupling a PDS device to the adjacentvertebrae, thereby providing a complete motion segment repair systemthat is implanted using a posterior surgical approach.

Posterior Distraction

FIG. 4 illustrates one exemplary method for distracting two adjacentvertebrae for implanting a disc implant therebetween. In general, themethod includes implanting a first pair of distraction anchors (only oneanchor 420 a is shown) in opposed lateral sides of a first vertebra 430a, and implanting a second pair of distraction anchors (only one anchor420 b is shown) in opposed lateral side of a second vertebra 430 b. Thedistraction anchors can be implanted using techniques known in the art,for example, by drilling holes in the vertebrae for receiving theanchors at the desired implant site. Once the anchors are implanted,they can used to distract the vertebrae to create space for the discimplant. The anchors can also receive bone screws (only two bone screws410 a, 410 b are shown) there over to allow a PDS device to be attachedto the vertebrae 430 a, 430 b.

Various devices known in the art can be used to engage the anchors anddistract the vertebrae. By way of non-limiting example, FIGS. 5A-5Cillustrate exemplary prior art distraction devices. In the embodimentshown in FIG. 5A, the device 500 includes opposed jaws 502 a, 502 b thathave ends 504 a, 504 b that are configured to engage the distractionanchors. The opposed jaws 502 a, 502 b are coupled to one another at apivot point 510, and to first and second arms 508 a, 508 b which, whenmoved together, will open the jaws. In use, the opposed jaws 502 a, 502b are positioned between the distraction anchors such that thedistraction anchors are received within an outer portion of each jaw 502a, 502 b. The first and second arms 508 a, 508 b are then squeezed toopen the opposed jaws 502 a, 502 b to separate the anchors, therebydistracting the vertebrae. The device 500 also includes a ratchet 512coupled to the arms 508 a, 508 b for holding the opposed jaws 502 a, 502b in an open position, thereby to allowing a disc implant to be insertedbetween the distracted vertebrae.

FIG. 5B illustrates another embodiment of a distraction device 530 thatcan be used to distract adjacent vertebrae with distraction anchorsimplanted on a posterior side of the vertebrae. As shown, the device 530is similar in configuration to the device 500 shown in FIG. 5A, exceptthat the device 530 of FIG. 5B includes a crossbar assembly 532 forsupporting the opposed jaws. The crossbar assembly 532 has first andsecond bars 534, 536 that are connected to one another by a pivot anchor538, and that each have first and second ends 540, 542, 544, 546 thatmate to the jaws. In particular, the second ends 544, 546 are mated tothe jaws at a fixed point, while the first ends 540, 542 are slidablymoveable within slots 548, 550 located on the opposed jaws. In use, theopposed jaws are positioned between the distraction anchors and thehandle is squeezed to open the opposed jaws to separate the anchors.

FIG. 5C illustrates another embodiment of a prior art distraction devicethat can be used to distract the anchors shown in FIG. 4. As shown, thedevice 560 includes a first member that is generally L-shaped with afirst arm 562 having first and second 566, 568, and an extension member574 extending from the second end 568 of the first arm 562. A second arm564 is slidably coupled to the extension member 574 at a second endthereof 572 by a housing 576, and it extends substantially parallel tothe first arm 562 such that a first end 566, 570 of each arm 562, 564can be used to engage and separate the distraction anchors. The device500 can also include markings formed on the extension member 574 forindicating a distance d between the first and second arms 562, 564during distraction, as well as a crank 578 that can be turned to movethe second arm 564 along the extension member 574. In use, the first andsecond ends 566, 570 are coupled to the distraction anchors and thecrank 578 is rotated to separate the first and second arms 562, 564,thereby separating the distraction anchors and distracting the adjacentvertebrae to allow for insertion of a disc implant therebetween.

While FIGS. 5A-5C are configured to engage distraction anchors, thedevices can be configured to engage one or more bone anchors implantedover the distraction anchors. As previously described, FIG. 4illustrates cannulated bone screws 410 a, 410 b that can be guided overthe distraction anchors 420 a, 420 b and threaded into the vertebrae 430a, 430 b. Additional bone screws can be implanted over additionaldistraction anchors implanted on the opposed lateral side (not shown) ofthe vertebrae. Alternatively, the bone screws or other bone anchors canbe implanted over the distraction anchors after distraction andimplantation of the disc implant has occurred.

A person skilled in the art will appreciate that a variety of otherdistraction methods can be used. For example, the bone screws can beused directly for distraction without the use of anchors, or the bonescrews and/or anchors can be used as a secondary distraction means tofacilitate distraction using other methods and devices. Distraction canalso optionally be achieved within the disc space. FIGS. 5D and 5Eillustrate one exemplary embodiment of a method for directly distractinga disc space using a multi-piece disc implant. As shown in FIG. 5D, thecontralateral side of a disc space is distracted using a distractiontool 580, and a first portion 590 a of a disc implant is partially orfully inserted into the ipsilateral side of the disc space. Thedistractor 580 is then removed, and the second portion 590 b of the discimplant, if necessary, is implanted into the contralateral side of thedisc space, as shown in FIG. 5E. Where a single piece disc implant isused, the disc implant can be partially inserted on the ipsilateral sidewhen the contralateral side is distracted. The distractor is thenremoving allowing the disc implant to be fully inserted into its finalposition between the adjacent vertebrae. As indicated above, the anchorsand/or bone screws could optionally be used to aid in distracting thevertebrae. A thin distractor, such as the distractor 595 shown in FIG.5F, could also optionally be used on the same side of the disc spacethat the disc implant is being introduced into to aid in insertion andpositioning of the disc implant.

Intra-Operative Manipulation of the Spinal Segment

In other embodiments, the anchors and/or bone screws used to couple aPDS device to adjacent vertebrae can be used to facilitateintraoperative manipulation of the spinal segment. For example, theanchors and/or bone screws can be implanted prior to distractingadjacent vertebrae and prior to implanting a disc implant and PDSdevice, and they can be used to restore normal anatomic alignment, suchas the reduction of a listhesis or other deformity or degenerativecondition in preparation for implantation of a disc implant. In otherembodiments, a temporary rigid device or the PDS device itself could beused to secure the vertebrae in a desired orientation duringimplantation of a disc implant. For example, a rigid device or the PDSdevice can be used to maintain the vertebrae in a desired orientation onone side of the vertebrae while implanting at least a portion of thedisc implant to be implanted between the disc space on the other side ofthe vertebrae. The mechanical resistance of the disc implant and/or PCTcan also help maintain the restored anatomic alignment, as the discimplant and/or PDS device can be configured to resist anterior shear.This is particularly advantageous for patients with spondylolisthesis.

Posterior Implant Insertion

Various methods and devices are also provided for positioning a discimplant between adjacent vertebrae using a posterior surgical approach.These methods and devices can be used in conjunction with the methodsand devices previously described for distracting adjacent vertebrae, orthey can be used alone to implant the disc implant and distract thevertebrae simultaneously.

FIGS. 6A-7B illustrate various techniques for introducing a disc implantinto a disc space between adjacent vertebrae using a posterior surgicalapproach. In an exemplary embodiment, as shown in FIG. 6A, a discimplant is positioned on the anterior side of a disc space betweenadjacent vertebrae using a posterior approach. The implant can then bepulled in a posterior direction using, for guidewire, to position theimplant at a desired location between the vertebrae. Pulling the implantin the posterior direction can be effective to further distract theposterior disc space, or alternatively one of the distraction techniquespreviously described can be used.

Once the implant is positioned in the anterior portion of the discspace, the implant can be pulled in a posterior direction to positionthe implant within the disc space. One exemplary technique for movingthe disc implant in a posterior direction is shown in FIGS. 6A and 6B.As shown in FIG. 6A, a guidewire 604 is positioned around the anteriorside of a disc implant 600 by feeding the guidewire 604 posteriorlybetween the superior vertebra 614 (shown in FIG. 6B) and the inferiorvertebra 602 through a first lateral side and pulling the guidewire outof the opposed lateral side. U.S. patent application Ser. No. 11/055,566filed on Feb. 10, 2005 and entitled “Intervertebral Prosthetic Disc AndMethod For Installing Using A Guidewire,” illustrates an exemplarytechnique for positioning a guidewire around a disc implant.

Once the guidewire is positioned around the implant, the opposed ends ofthe guidewire can be used to pull the implant in the posteriordirection. While a pulling force can be applied directly to theguidewire, or a cable tensioning device can be used, in one exemplaryembodiment, as shown in FIG. 6A-6B, the distraction anchors are used toredistribute the load necessary to move the implant. In particular, afirst support plate 610 can coupled to a first pair of distractionanchors 606, 616 (shown in FIG. 6B) implanted on a first lateral side ofthe vertebrae, and a second support plate 612 can be coupled to a secondpair of distraction anchors (only one distraction anchor 608 is shown inFIG. 6A) implanted in a second lateral side of the vertebrae. Each plate610, 612 can have a variety of shapes and sizes, but in the illustratedembodiment each plate 610, 612 includes superior and inferior bores(superior and inferior bores 613 a, 613 b on plate 610 are shown in FIG.6B) for receiving the distraction anchors 606, 616, and a central bore618 through which the guidewire 604 can be passed to direct the loadalong the axis of the distraction anchors. Once the guidewire is passedthrough the plates 610, 612, the ends of the guidewire 604 can be pulledusing, for example, a cable tensioning device, to move the implant 600in a posterior direction and thereby position the implant between theadjacent vertebrae. Pulling the implant in a posterior direction canalso be effective to further distract the posterior disc space, oralternatively, one of the distraction techniques previously describedcan be used. Distracting the vertebrae using the implant and the supportplates allows the load to be directed along the axis of each distractionanchor and eliminates the need to distract using the anchors asdistraction can cause the distraction anchors to loosen. While thesupport plates are described for use with the distraction anchors, thesupport plates can also be configured to be disposed over the bonescrews.

A variety of devices can be used to position a disc implant in the discspace using a posterior approach. FIGS. 7A-7B show one embodiment of aguide device that is effective to slide a disc implant 710 (shown inFIG. 7B) into a disc space. As shown, the guide device 700 includesopposed arms 702 that form an elongate pathway therebetween for seatinga disc implant 710. The proximal end 704 of the arms 702 can be curvedto guide the implant 710 as it is directed along the pathway and intothe disc space. The arms of the device may also be used to initiatedistraction of the disc space. The device 700 can also include a handlehousing 716 to facilitate grasping of the device, and a pusher shaft 708extending through the handle housing 716 and between the opposed arms702 for pushing the implant 710 along the pathway and into the discspace. The housing 716 can also include a trigger 718 formed thereon andmovably coupled thereto for advancing the pusher shaft 708 between theopposed arms 702 to insert the implant 710 into the disc space. In use,the implant 710 is positioned between the opposed arms 702, and thetrigger 718 is squeezed to drive the pusher shaft 708 distally, therebydriving the implant 710 along the pathway. As the implant 710 is guidedalong the pathway, the curved distal end 704 will cause the implant 710to pivot so that it can be advanced into the disc space. Furtherpositioning should not be required, but if needed, it may be done usingthe guide wire technique described previously.

In another embodiment, shown in FIG. 8, a guide device 800 can be usedto position a disc implant in the disc space without the need to pullthe implant in a posterior direction. Distraction may be achieved viaseveral methods, but in an exemplary embodiment, distraction isperformed in the disc space on the contralateral side. As shown in FIG.8, the device 800 has a generally elongate shape with a pivoting member810 formed on a distal end 806 thereof. The pivoting member 810 isconfigured to engage a disc implant 812 and to pivot the disc implantinto position between a superior and inferior vertebrae (only inferiorvertebra 802 is shown). A variety of techniques can be used to engagethe implant including, for example, a threaded member, a dovetailconnection, opposed arms, etc. The device can also include an actuationmechanism 814 formed on a proximal end 808 thereof for actuating thepivoting member 810, and a release mechanism (not shown) to release theimplant from the pivoting member 810. In the illustrated embodiment, thedevice 800 includes a rotatable actuation mechanism 814 that is coupledto a gear assembly disposed within the distal portion of the elongateshaft and effect to pivot the implant. In use, the distal end 806 isinserted into the disc space between the superior and inferior vertebraeusing a posterior approach. The turning mechanism 814 is rotated topivot the implant 812 into position between the superior and inferiorvertebrae, and then the release mechanism releases the implant into thedisc space.

PDS Device Placement

Various methods and devices are also provided for coupling a PDS device(ranging from a dynamic stabilizer to a complete facet replacement) toadjacent vertebrae using a posterior surgical approach. After the discimplant is inserted into the disc space between two adjacent vertebraeand positioned using the exemplary methods and devices described above,a PDS device can be attached to the vertebrae using bone anchors toprovide a full motion segment repair system. As previously mentioned, atleast one of the PDS device and the disc implant can have a floatingcenter of rotation to allow the PDS device to be implanted at variouslocations relative to the vertebrae. However, it may be necessary tomeasure a depth of the disc implant within the disc space to facilitateselection and/or positioning of the PDS device.

Accordingly, FIGS. 9A-9B illustrate one embodiment of a depth gaugeindicator 900 that can be used to determine proper size and/or placementof a PDS device based on a depth of a disc implant 902 disposed betweensuperior and inferior vertebrae 904, 906. As shown, the indicator 900includes has a generally elongate shaft with a distal end is adapted tobe inserted between the adjacent vertebrae to the location of the discimplant, and a proximal portion with markings 910 formed thereon. Thedevice can also include a handle 908 to facilitate grasping. As isfurther shown, the device includes an extension member 914 that isslidably coupled to the proximal portion and that is adapted to bereceived within the head of a bone anchor 912. The position of theextension member 914 relative to the markings 910 can indicate the depthD of the implant 902. This depth can then be used to select a PDS devicehaving the appropriate size and/or to position the PDS device.

One of ordinary skill in the art will appreciate further features andadvantages of the invention based on the above-described embodiments.Accordingly, the invention is not to be limited by what has beenparticularly shown and described, except as indicated by the appendedclaims. All publications and references cited herein are expresslyincorporated herein by reference in their entirety.

1. A method for implanting a motion segment repair system, comprising:inserting a guide device into a disc space between adjacent superior andinferior vertebrae using a substantially posterior surgical approach,the guide device having a disc implant movably coupled to a distal endthereof; actuating the guide device to pivot the disc implant within thedisc space and thereby position the disc implant between adjacentsuperior and inferior vertebrae; and coupling a posterior stabilizationdevice to the adjacent superior and inferior vertebrae.
 2. The method ofclaim 1, wherein at least one of the disc implant and the posteriorstabilization device has a floating center of rotation to allow theposterior stabilization device to be positioned at various locationsrelative to the adjacent superior and inferior vertebrae.
 3. The methodof claim 2, wherein the disc implant has a floating center of rotation.4. The method of claim 3, wherein implanting the disc implant comprisesimplanting first and second end plates with a central core moveablydisposed therebetween between the adjacent superior and inferiorvertebrae.
 5. The method of claim 2, wherein the posterior stabilizationdevice has a floating center of rotation.
 6. The method of claim 5,wherein coupling the posterior stabilization device to adjacent superiorand inferior vertebrae comprises coupling a first connector of theposterior stabilization device to the superior vertebra and coupling asecond connector of the posterior stabilization device to the adjacentinferior vertebrae, the first and second connectors being movably matedto one another by a flexible member to allow motion between the adjacentsuperior and inferior vertebrae.
 7. The method of claim 2, wherein theposterior stabilization device has a floating center of rotation.
 8. Themethod of claim 2, wherein the posterior stabilization device has afixed center of rotation.
 9. The method of claim 8, wherein coupling theposterior stabilization device to adjacent superior and inferiorvertebrae comprises coupling a first connector of the posteriorstabilization device to the superior vertebra and coupling a secondconnector of the posterior stabilization device to the adjacent inferiorvertebrae, the first and second connectors being slidably coupled to oneanother to allow at least some flexion and extension between theadjacent superior and inferior vertebrae.
 10. The method of claim 2,wherein the floating center of rotation is adapted to allow at leastsome flexion, extension, lateral bending, and axial rotation between theadjacent superior and inferior vertebrae.
 11. The method of claim 1,further comprising, prior to inserting, distracting the adjacentsuperior and inferior vertebrae using one or more distraction anchorsdisposed in a posterior side of the adjacent superior and inferiorvertebrae.
 12. The method of claim 1, further comprising, prior tocoupling a posterior stabilization device, measuring a distance betweenthe disc implant and at least one anchoring element implanted in aposterior surface of the adjacent superior and inferior vertebrae, andusing the measured distance to select a posterior stabilization devicehaving an appropriate size.
 13. The method of claim 1, furthercomprising actuating a release mechanism on the guide device to releasethe disc implant from the guide device.
 14. A method for implanting amotion segment repair system, comprising: distracting a first side of adisc space formed between the adjacent superior and inferior vertebrae;inserting a disc implant into an opposed second side of the disc spaceusing a substantially posterior approach, the disc implant being coupledto a distal end of a guide device; actuating the guide device to pivotthe disc implant within the disc space and thereby position the discimplant between adjacent superior and inferior vertebrae; and removingthe distractor tool.
 15. The method of claim 14, further comprisingcoupling a posterior stabilization device to the adjacent superior andinferior vertebrae.
 16. The method of claim 14, wherein actuating theguide device comprises rotating a rotatable actuation mechanism on theguide member.
 17. The method of claim 14, further comprising actuating arelease mechanism on the guide device to release the disc implant fromthe guide device.
 18. A method for implanting a motion segment repairsystem, comprising: introducing a guide device into a disc space using aposterior surgical approach to position a disc implant coupled to adistal end of the guide device on a first lateral side of the discspace; actuating a mechanism on a proximal end of the guide device topivot the disc implant within the disc space; and actuating a releasemechanism on the guide device to release the disc implant from thedistal end of the guide device.
 19. The method of claim 18, furthercomprising coupling a posterior dynamic stabilization device to aposterior side of adjacent superior and inferior vertebrae surroundingthe disc space.